WASHINGTON (CNN) -- U.S. Defense Secretary Robert Gates, criticized by some for comments indicating NATO forces in southern Afghanistan are not up to par, praised them Thursday for their "valor and sacrifice," which has caused the Taliban "significant losses."

U.S. Defense Secretary Robert Gates had originally said NATO as a whole was not trained for counterinsurgency.

He also assured other countries that the planned deployment of of 3,200 Marines to Afghanistan this spring is not because of any shortcomings by forces already there. The troops were requested by the International Security Assistance Force.

"It reflects the fact that NATO and U.S. commanders believe they need more troops to take advantage of last year's military successes "to keep the pressure on the Taliban and to accelerate the training of the Afghan national security forces," Gates said.

The deployment does not reflect dissatisfaction with Afghan operations, he said at a news conference, also attended by Gen. James Cartwright, vice chairman of the Joint Chiefs of Staff.

"There have been several recent media reports of discontent in the United States and among other NATO members about operations in Afghanistan. This does not reflect reality or, I believe, the views of our governments," Gates said.

"As I said before the House Armed Services Committee last month, allied forces from the United Kingdom, Canada, Netherlands, Australia, Denmark and other nations have stepped up to the plate and are playing a significant and powerful role in Afghanistan.

"They have rolled back the Taliban from previous strongholds in the south. They are taking the fight to the enemy in some of the most grueling conditions imaginable.

"As a result of the valor and sacrifice of these allies, the Taliban has suffered significant losses, and no longer owns any real estate of any consequence."

The newest Marines will help train Afghanistan's national security force, he said, and other fighters.

Gates added: "We have to acknowledge the reality that the alliance as a whole has not trained for counterinsurgency operations, even though individual countries have considerable expertise."

Don't Miss

The secretary's earlier comments about NATO troops caused a stir in Canada and Europe. The Dutch defense minister asked the U.S. ambassador for an explanation, and Canadian leaders conferred with their U.S. counterparts.

The Los Angeles Times quoted Gates on Wednesday as saying that some NATO troops in southern Afghanistan lack the know-how to combat insurgents.

"I'm worried we're deploying (military advisers) that are not properly trained and I'm worried we have some military forces that don't know how to do counterinsurgency operations," the newspaper quoted Gates as saying.

Troops from Canada, the Netherlands and the United Kingdom operate alongside U.S. forces in southern Afghanistan, where the Taliban has recently gained strength.

In comments published Wednesday, Gates said that "most of the European forces, the NATO forces, are not trained in counterinsurgency" but have trained instead to defend against a Cold War threat -- a potential Soviet invasion of Western Europe.

Pentagon spokesman Geoff Morrell said that Gates telephoned Dutch Minister of Defense Eimert van Middelkoop on Thursday "to clear up the misunderstanding caused by the article and express regret for the difficulties it has caused (the) Dutch."

In Canada, U.S. Ambassador David H. Wilkins also reiterated U.S. support for Canadian troops in Afghanistan. He noted Wednesday that he spent Christmas with the Canadian armed forces in Afghanistan.

"These troops are heroes," he said in a statement posted on the Embassy Web site. "They are doing remarkable and effective work in Afghanistan under the toughest of circumstances."

Gates personally called the Canadian defense minister, Peter MacKay, to explain his remarks.

"He said, 'I specifically made no reference to any country, and Canada is the last country that I would make those comments about. They were not meant to be disparaging, disrespectful or in any way to diminish the effort which Canada has put forward,'" MacKay said in comments broadcast on the Canadian Broadcasting Corporation.

Britain's Ministry of Defense was unruffled by Gates' comments, and issued a statement saying, "We are confident that the commander of ISAF, U.S. General Dan McNeill, is more than content with the UK forces operating in Southern Afghanistan."

"We have a good working relationship with the U.S. and other NATO allies," the MoD statement said.

"UK forces have extensive experience in counterinsurgency, and work closely with the U.S. and other ISAF partners and the Afghan national security forces."